1. Field of the Invention
The present invention relates to an electronic oscillation signal generation circuit, and more particularly, to an electronic oscillation signal generation circuit utilizing a counter and a delay unit for maintaining amplitude and a period of an electronic oscillation signal.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram showing an electronic oscillation signal generation circuit 100 of the prior art. FIG. 2 is a diagram showing related signals of the electronic oscillation signal generation circuit 100 of FIG. 1. The electronic oscillation signal generation circuit 100 of the prior art comprises an electronic oscillation circuit 110, a charging capacitor Cv, a switch T, a conversion circuit 120, a counter 130, a measurement unit 140, and a pulse signal generation circuit 150. The electronic oscillation circuit 110 comprises an inductor L and a capacitor C. The inductor L and the capacitor C are electrically connected to each other in parallel. The charging capacitor Cv is electrically connected to a first end of the electronic oscillation circuit 110 for providing a DC voltage to the electronic oscillation circuit 110. The switch T is for electrically connecting a second end of the electronic oscillation circuit 110 to ground G when the switch T is turned on, in order to allow electricity to flow to ground G from the charging capacitor Cv through the electronic oscillation circuit 110. When the switch T is turned off thereafter, the electronic oscillation circuit 110 generates an analog oscillation signal. The analog oscillation signal is generated from a trough position. The conversion circuit 120 is electrically connected to a second end of the electronic oscillation circuit 110 for converting the analog oscillation signal of the electronic oscillation circuit 110 to a digital oscillation signal.
However, amplitude of the analog oscillation signal decreases gradually due to resistance of the inductor L of the electronic oscillation circuit 110. In order to prevent the analog oscillation signal from over-decaying, the electronic oscillation signal generation circuit 100 of the prior art utilizes the counter 130, the measurement unit 140, and the pulse signal generation circuit 150 to turn on and turn off the switch T again when the analog oscillation signal reaches a predetermined number of periods, so as to generate a new analog oscillation signal. As shown in FIG. 1, the counter 130 is electrically connected to the conversion circuit 120 for counting the number of periods of the digital oscillation signals and generating a control signal when the digital oscillation signal reaches a predetermined number of periods. The measurement unit 140 is electrically connected to the electronic oscillation circuit 110 for measuring voltage level of the analog oscillation signal. The pulse signal generation circuit 150 is electrically connected to the counter 130 and the measurement unit 140. The pulse signal generation circuit 150 generates a pulse signal to turn on the switch T when the voltage level of the analog oscillation signal reaches a voltage level of the trough position after receiving the control signal of the counter 130. The switch T is turned off again immediately when the pulse signal disappears. Accordingly, the electronic oscillation circuit 110 generates a new analog oscillation signal in order to replace the old analog oscillation signal.
In the above arrangement, the measurement unit 140 needs to detect precisely when the analog oscillation signal reaches the trough, otherwise the new analog oscillation signal can not replace the old analog oscillation signal in the trough position (where an analog oscillation signal starts from), and the period of the digital oscillation signal is changed accordingly. However, the amplitude of the analog oscillation signal decreases gradually due to the resistance of the inductor L, that is, a peak value of the trough of the analog oscillation signal changes over time. Therefore, the electronic oscillation signal generation circuit 100 of the prior art can not precisely detect when the analog oscillation signal reaches the trough, and thus makes the period of the digital oscillation signal unstable. In addition, the measurement unit 140 needs to keep measuring the voltage level of the analog oscillation signal all the time, such that the electronic oscillation signal generation circuit 100 has more power consumption.